Parallel connections for unsophisticated users and installers

For unsophisticated users and installers when connecting in parallel, only use new and identical batteries.

If you connect two 12-volt batteries in parallel and they are identical in type, age and capacity, you can potentially double your original capacity. If you connect two that are not the same type, you will either overcharge the smaller of the two, or you will undercharge the larger of the two. If you connect two identical – but one older – you will definitely reduce the life of the new one.

When connecting in series or parallel and to prevent recharging problems, do not mix old and new batteries or ones of different chemistries or performance abilities. Cable lengths should be kept short and cabling must be sized large enough to prevent significant voltage drops. There should be a maximum drop of 0.2 volts (200 milli-volts) between batteries.

To increase the voltage of a system you must connect multiple batteries in Series (See Figure 3).